Obstacle

About: Obstacle is a research topic. Over the lifetime, 9517 publications have been published within this topic receiving 94760 citations. The topic is also known as: impediment & barrier.

Computational analysis and flow structure of a transitional separated-reattached flow over a surface mounted obstacle and a forward-facing step

Abstract: Large-eddy simulation (LES) of transitional separating-reattaching flow on a two-dimensional square surface mounted obstacle and a forward facing step has been performed using a dynamic sub-grid scale model. The Reynolds number based on the uniform inlet velocity and the obstacle/step height is 4.5 × 103. The mean LES results for both the obstacle and step flow compare reasonably well with the available experimental and DNS data. The flow structures upstream of the surface-mounted obstacle (referred to hereafter as obstacle) and the forward-facing step (referred to hereafter as FFS) consist of unstable two-dimensional structures and coherent rib-shaped structures. These structures with the aid of 3D streamline visualisation strongly indicate that the upstream separation bubble is a closed one rather than an open one in the sense that there is little evidence to suggest that there is fluid injection from the upstream separation region into the downstream separated region for the two geometries. The spectra and time history for the velocities and pressure fields at locations immediately upstream of the obstacle and FFS (including the recirculation region) were analysed using both the Fourier and wavelet transforms and revealed the unsteady nature of the recirculation region upstream of the obstacle and FFS. The transition process has been elucidated using both 2D and 3D flow visualisation of the flow. In both geometries (obstacle and FFS), the separated boundary layer downstream of the leading edge shows 2D nature and roll-up shortly downstream of the separation line leading to 2D K-H rolls to be shed from the leading edge. Coherent structures such as the λ-shaped and rib-like vortices commonly associated with a flat plate boundary layer and also found in the separated-reattached flow of a blunt leading edge plate aligned horizontally to a flow are not common in the separated-reattached flow over the obstacle and FFS.

An Obstacle Control Problem with a Source Term

Abstract: . An optimal control problem for an elliptic variational inequality with a source term is considered. The obstacle is the control, and the goal is to keep the solution of the variational inequality close to the desired profile while the H 1 norm of the obstacle is not too large. The addition of the source term strongly affects the needed compactness result for the existence of a minimizer.

Instantaneous impact point based unmanned aerial vehicle non-collaborative real-time obstacle avoidance method

Abstract: The invention discloses an instantaneous impact point based unmanned aerial vehicle non-collaborative real-time obstacle avoidance method. The instantaneous impact point based unmanned aerial vehicle non-collaborative real-time obstacle avoidance method comprises the steps of 1 performing obstacle detection, namely obtaining a relative motion state of an obstacle, 2 performing obstacle motion estimation, namely obtaining machine state information based on satellite navigation information and calculating a motion state of an inertial space obstacle, 3 performing impact conflict detection, namely judging whether obstacle impact occurs or not, 4 performing obstacle avoidance decision making, namely making an obstacle avoidance decision based on a detection result in the step 3, 5 performing obstacle avoidance route re-planning based on a quick expanding random tree algorithm considering an instantaneous impact point, namely introducing route evaluation heuristic information based on the instantaneous impact point and achieving obstacle avoidance route re-planning. The instantaneous impact point based unmanned aerial vehicle non-collaborative real-time obstacle avoidance method has the advantages of being simple in principle, easy to achieve, capable of improving unmanned aerial vehicle safety and the like.

Obstacle detection from IPM and super-homography

Abstract: We present in this article a simple method to estimate an IPM view from an embedded camera. The method is based on the tracking of the road markers assuming that the road is locally planar. Our aim is the development of a free-space estimator which can be implemented in an Autonomous Guided Vehicle to allow a safe path planning. Opposite to most of the obstacle detection methods which make assumptions on the shape or height of the obstacles, all the scene elements above the road plane (particularly kerbs and poles) have to be detected as obstacles. Combined with the IPM tranformation, this obstacle detection stage can be viewed as the first stage of a free-space estimator dedicated to AGV in the complex urban environments.

Control method and apparatus for free-running mobile unit

Abstract: PROBLEM TO BE SOLVED: To enable performing appropriate avoidance actions by creating a movement route for a mobile unit in response to movements of obstacles even when there exist obstacles in motion. SOLUTION: An obstacle sensor 3 attached on a ceiling surface detects sequentially positions of an obstacle 2 to transfer to a control device 10. The control device 10 creates a probability potential field indicating a probability of existence of obstacles and adds a gradient headed to a target position in the potential field. The control device 10 then searches a route headed to the target position according to the gradient of the potential field added the gradient and moves a mobile unit 1 along the searched route. So that the potential field is created, it is possible to predict future motion of the obstacles in the motion and avoid the obstacles. And data from the sensor 3 is processed in a probabilistic way, so that it is possible to acquire the probability of existence of the obstacles at the next time without being influenced on fluctuations of the data from the sensor 3. COPYRIGHT: (C)2003,JPO